Dec. 28, 2011 -- Eating a diet rich in certain vitamins and omega-3 fatty acids and low in trans fats may be best for brain health, new research suggests.

Older people who ate this way had less of the brain shrinkage linked with Alzheimer's disease and scored better on mental and thinking tests than those with poorer diets.

Although previous studies have suggested that a heart-healthy diet is also good for the brain, the new study took a different approach by using blood tests to determine the participant's diet and nutrient levels.

Diets high in omega-3 fatty acids, found in fish, were also good for brain health.

Most unfavorable, he found, was a diet high in trans fats. Trans fats are more often found in packaged baked goods and fast foods, including cookies, crackers, and potato chips.

B vitamins are found in a variety of foods, such as milk and dairy, whole grain cereals, enriched bread, and peanut butter. Vitamin C is rich in fruits and vegetables, and E is in nuts and oils. Vitamin D is found in the flesh of fatty fish, such as salmon, and in fortified milk.

For the vitamins, omega-3s, and trans fats, Bowman found an association between diet and brain health, not cause and effect.

The study is published online in the journal Neurology.

Diet and Brain Health: Results

The average age of those studied was 87. They had very few risk factors known to boost the risk of memory and thinking problems, such as diabetes or high blood pressure.

Besides the blood tests, the men and women were given memory and thinking skills tests. Forty-two had MRI scans to measure brain volume. Decreased brain volume has been linked with declines in thinking ability associated with Alzheimer's disease. The researchers evaluated how much of the risk of declining mental abilities could be attributed to diet and how much to other factors, such as age or high blood pressure.

The team looked at 30 different nutrient biomarkers. Those most consistently linked to brain health were the vitamins, omega-3 fatty acids, and trans fats.

The declines in mental and thinking ability were attributable more to age and other risk factors, but diet did seem to play a role. For the variation found in the tests of mental and thinking abilities, Bowman's team found risk factors such as age explained about 46% of the variation. Diet explained less, about 17%, Bowman says.

For the variation in brain volume, diet seems to matter as much as the other risk factors. Diet explained about 37% of the variation, he says. The other risk factors explained about another 40%.

The study was looking just at one point in time, Bowman says, which is a limitation of the study. "We can't say these patterns predict rate of change over time."

Diet and Brain Health: Perspective

As the research progresses, the study results suggest someday it may be possible to slow cognitive declines through diet, Christy Tangney, PhD, associate professor of clinical nutrition at Rush University Medical Center, Chicago, tells WebMD. She wrote an editorial to accompany the study.

Down the road, she says, the researchers might use a blood measure that reflects a typical diet, not just a point in time.

However, she says, it is encouraging that their results are similar to those in other studies that looked at diet and brain health but used questionnaires instead of a blood test.

Another study limitation is its small size and that the people studied were not diverse, says Heather Snyder, PhD, senior associate director of medical and scientific relations for the Alzheimer's Association. She reviewed the study findings.

Until more research is done, she says eating a heart-healthy diet -- which may also help your brain -- is the best advice.

Bowman agrees that the standard advice to eat more fruits and vegetables and fish and avoid trans fats seems wise. Omega-3 fatty acids and vitamin D are found in fish. The B, C, and E vitamins he linked with less brain shrinkage are in fruits and vegetables.

Look at nutrition labels to see if foods contain trans fats, Bowman says.

Bowman serves on the editorial board of the Journal of Alzheimer's Disease. Some co-authors report receiving honoraria for speaking or consulting from Pfizer, Novartis, and other companies and funds for research from Baxter International Inc., Bristol-Myers Squibb, and other companies.